Jun 10, 2015, 06:49 PM
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New DI Engines -- Excessive Carbon Buildup ??
Senior Member
Joined: Aug 2019
Posts: 284
Likes: 77
2019 GLC300, 2017 E300
Came across this thread researching carbon buildup relative to my wife's GLC300 (M274). As far as the catch can goes..
I have a daily driver Hyundai Accent 1.6 GDI. @ 7.5k miles I installed a Jegs Air/Oil separator. At 11k, I did a valve cleaning with the CDC GDI IVD cleaner. Tons of white smoke. Repeated at 22k and similar results, less smoke. Repeated at 33k, very little to no smoke. I'm at 65k and about to repeat.. but that little air/oil separator collects ~1 tbsp. every ~600 miles. Running Amsoil OE synthetic and top tier fuel. I haven't scoped the intake tract, but the car runs like a top. I've heard of others having issues, so I wanted to be proactive.
Searching for a catch can kit for the GLC, although the stock oil separator system seems pretty decent. It recirculates the oil back to the engine though vs. draining.. planning on more frequent intervals for oil changes (she currently has 3.5k miles on it) to prevent issues in the future.
I have a daily driver Hyundai Accent 1.6 GDI. @ 7.5k miles I installed a Jegs Air/Oil separator. At 11k, I did a valve cleaning with the CDC GDI IVD cleaner. Tons of white smoke. Repeated at 22k and similar results, less smoke. Repeated at 33k, very little to no smoke. I'm at 65k and about to repeat.. but that little air/oil separator collects ~1 tbsp. every ~600 miles. Running Amsoil OE synthetic and top tier fuel. I haven't scoped the intake tract, but the car runs like a top. I've heard of others having issues, so I wanted to be proactive.
Searching for a catch can kit for the GLC, although the stock oil separator system seems pretty decent. It recirculates the oil back to the engine though vs. draining.. planning on more frequent intervals for oil changes (she currently has 3.5k miles on it) to prevent issues in the future.
Junior Member
Joined: Jan 2018
Posts: 28
Likes: 5
From: South Florida
Mercedes Benz C250 Sedan 2012
Hey there Guys if anybody is still following this thread! I have noticed that my C250 ( M271 EVO) had rough idle and was sluggish.
if You disconnect the intercooler hose and use SPRAY seafoam and gentley spray it into the throttlebody while the engine is idling, it will do the job.
After finifishing about half a bottle of seafoam, one should let the car sit for about 15 minutes and then start reving the engine till 4000rpm.....
It cleaned my dirty throttle body and apparently removed plenty of carbon!
MBWorld Fanatic!
Joined: Aug 2017
Posts: 1,696
Likes: 521
2019 S560, 2015 Honda Civic Hybrid
The carbon build up is in the intake passages in the cylinder head and comes from crankcase (oil) vapors recirculated into the intact tract. You may have a dirty throttle body, but it isn't from recirculated oil vapor because the TB is upstream from there.
Joined: Nov 2016
Posts: 7,847
Likes: 3,496
From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
My head was about to explode �� after the first hour of reading this thread. So, I will just add in my recent experience.
I removed the intake plenum on my 2014 C350 (276.957) engine at ~60,000 miles to replace the spark plugs. I checked the intake valves and notice some carbon buildup, but not too bad. I didn’t have everything I needed, so I put it back together for another try. In the mean time, I used the CRC intake treatment and the a day later, I used Gumout 510011 Multi-System Tune-Up through the vacuum purge line hole just past the throttle body.
When I went back in to change the plugs, I noticed the valves looked much better. There was still some carbon on the back of the valves, but not as much. And, there was nothing on the valve stems. I plan on repeating the Gumout treatment every 5000 miles.
The one one thing I found encouraging was that after 60,000 miles, the buildup looked nothing like some of the pictures at the beginning of this thread.
I removed the intake plenum on my 2014 C350 (276.957) engine at ~60,000 miles to replace the spark plugs. I checked the intake valves and notice some carbon buildup, but not too bad. I didn’t have everything I needed, so I put it back together for another try. In the mean time, I used the CRC intake treatment and the a day later, I used Gumout 510011 Multi-System Tune-Up through the vacuum purge line hole just past the throttle body.
When I went back in to change the plugs, I noticed the valves looked much better. There was still some carbon on the back of the valves, but not as much. And, there was nothing on the valve stems. I plan on repeating the Gumout treatment every 5000 miles.
The one one thing I found encouraging was that after 60,000 miles, the buildup looked nothing like some of the pictures at the beginning of this thread.
